1. Field of the Invention
The present invention relates generally to a braking system for a right hand drive vehicle and more particularly to adaptation of a left hand drive vehicle braking system for a right hand drive vehicle.
2. Description of the Related Art
The conventional arrangement in the United States is for the vehicle driver to operate the vehicle from the left hand side of the vehicle. However, in countries such as England, Japan, and many others around the world, the driver operates the vehicle from the right hand side. In order for a vehicle manufacturer to simultaneously market and sell a particular vehicle model in the U.S. and a country with the right hand drive custom, various driver-actuated components such as the accelerator control system for controlling the speed of the vehicle, the braking system for stopping the vehicle, the steering wheel and column and the instrument panel have to be convertible between the left hand version and the right hand version.
It is advantageous to use as many common components as possible between a left hand drive system and a right hand system. This is not always possible, for example, space limitations may preclude the use of common components, or even the adaptation of one drive convention to the other.
The primary components of a typical power assisted brake system, commonly referred to as power brakes, used on a motor vehicle include a brake pedal, a master cylinder, a brake booster, and the individual brake mounted on each wheel. Power brakes are advantageous in that a vacuum operated brake booster is used to reduce the amount of force the driver must apply to the brake pedal in order the stop the vehicle. The brake booster is mounted o the engine side of the dash panel. Within the brake booster are valves actuated by a push rod externally connected to the brake pedal. As the brake pedal is depressed, the valves open and close to create a vacuum on one side of a diaphragm within the brake booster and allowing atmospheric pressure to enter on the other side. The pressure difference forces an output rod out of the brake booster against the primary piston of the master cylinder. As the piston in the master cylinder is moved, hydraulic pressure is created in the brake lines connecting the master cylinder to the individual brakes mounted on each wheel, causing the application of the brakes and a slowing down of the spinning of the wheels, until the vehicle stops.
The brake booster should be located in close proximity to the master cylinder as well as the brake pedal due to the mechanical interaction of these components. One way to adapt the brake system to right hand drive would be to reverse all brake system components from the left hand side of the vehicle to the right hand side. However, this is not always possible due to the relative size of the brake booster and master cylinder and space limitations within the engine and passenger compartments.
Another conventional arrangement is to mount the brake pedal on the right hand side of the vehicle as a mirror image of the left hand side location. The brake booster and master cylinder remain in the same location on the left hand side. One end of a torque rod is connected directly to the push rod extending from the brake booster and the other end is connected to the brake pedal. The torque rod translates the travel of the brake pedal from an at rest position, to a fully depressed position, or to any point in between, directly to the push rod.
Space limitations in the passenger compartment, for instance due to the air conditioning ductwork, may restrict placement of the brake pedal in a mirror image location on the right hand side as with a left hand drive location, or maintaining the same location of the brake booster. In this case, one option is to redesign the brake pedal. Another is to add additional linkage to the torque rod to achieve the same pedal geometry as with the left hand drive system.
Pedal geometry is the use of geometric concepts to relate the distance the push rod must travel to generate sufficient vacuum and hydraulic pressure to engage the brakes, the configuration of the brake pedal shaft, and the arc over which the brake pedal travels from an at rest position to a fully depressed position without encountering any obstacles, such as the vehicle floor. Pedal geometry may also affect pedal effort, or the amount of physical exertion required to depress the brake pedal.
A further consideration which may affect the design of the brake pedal is compliance with safety standards in the country in which the vehicle is sold. For instance, Federal Motor Vehicle Safety Standard 105, (54 FR 22905), hereby incorporated by reference, sets forth requirements that hydraulic brake systems must comply with including, minimum stopping distance and the amount of force required in applying the brakes to stop the vehicle.